A drive train of a motor vehicle has a drive unit, a transmission and an output, whereas the transmission is connected between the drive unit and the output. The transmission converts rotational speeds and torques, and thus provides the pulling power effort of the drive unit at the output. In order to start a motor vehicle, a starting element is closed, whereas the starting element to be closed typically comprises a frictional-locking shift element of the transmission, which, for starting, is closed in a slipping manner such that, during the closing process, the slip at the frictional-locking shift element serving as the starting element is reduced by a defined pressure control of the shift element until the frictional-locking shift element is completely closed and the slip thereon is completely degraded. Accordingly, during the starting process, the slip or a differential rotational speed at the frictional-locking shift element serving as the starting element is reduced. Upon the reduction of the differential rotational speed at the starting element, a resonance-critical range of rotational speeds is passed through. For this purpose, during the starting process, the drive train can be excited to form resonance vibrations, which causes an undesirable longitudinal vibration and undesirable noises.
WO 2009/109822 A1 discloses a method for operating a drive train of a hybrid vehicle, whereas the drive unit of the hybrid vehicle comprises an internal combustion engine and an electric motor, whereas a holding element formed as a frictional-locking clutch is connected between the internal combustion engine and the electric motor. In order to avoid vibrations and noises that may arise from resonances, it is proposed, according to this state of the art, to stop the internal combustion engine while the holding element, which is connected between the internal combustion engine and the electric motor, is engaged.
A control device for a vehicle drive system is known from DE 10 2005 036 518 A1. According to this state of the art, when the internal combustion engine is stopped, it is proposed to reduce resonance phenomena by lowering the rotational speed of an electric motor, in order to rapidly reduce the rotational speed of the internal combustion engine through a predetermined range of the resonance rotational speeds.